The overall objective of the proposed work is to delineate the relationship among dietary components, intraluminal bile acids and neutral sterols, intestinal microflora and colon cancer in man, and to develop a biochemical and/or bacterial indicator which distinguishes low and high risk populations for colon cancer. We analyzed feces collected for 72 hours from high risk Americans, low risk Japanese, and patients with colon cancer, familial polyposis, ulcerative colitis, and polyps, for neutral sterols, bile acids microflora and bacterial 7 gamma- dehydroxylase. Our data indicate that the patients with colon cancer and ulcerative colitis excreted high levels of bile acids and neutral sterols compared with high risk American controls. Low risk Japanese showed a decrease in fecal bile acid and neutral sterol excretion compared with high risk Americans. Bacterial 7 gamma-hydroxylase activity was higher in patients with colon cancer or polyps than in controls. The ratio of fecal anaerobes to aerobes was higher in patients with colon cancer or polyps than in controls.